1. Field of the Invention
The present invention relates to a printing element substrate and printhead.
2. Description of the Related Art
There is known a printing apparatus which adopts an inkjet printing method. This printing apparatus prints an image on a printing medium by discharging ink from printing elements arrayed on a printhead. Japanese Patent No. 4245848 discloses a printhead in which a feedback-amplifier controls power to be applied to the printing element to be constant.
To increase the printing operation speed, for example, the period of time to drive the printing element needs to be shortened to 1 μs or less. During the period of the time for driving the printing element, the feedback-amplifier adjusts the impedance of the driving element while detecting the voltage of the printing element, thereby controlling power to be applied to the printing element to be constant (feedback control).
However, to quickly perform feedback control within 1 μs or less, a bias current Ibias to be supplied to the feedback-amplifier needs to be increased. Since the bias current Ibias of the feedback-amplifier is a steady current, simply increasing the bias current Ibias results in large power consumption. Large power consumption raises the printhead temperature, affecting the image quality.